On the one hand, conventional, state-of-the-art turbine engines constantly lose energy on account of the required air compressing process (compressor work) ahead of the infeed into the combustion chamber. On the other hand, fuel must be injected constantly in order to safeguard the turbine function and operation, even if the turbine operates under low load. This leads to high energy consumption combined with a heavy environmental impact.
Piston engines make discontinuous fuel feed possible. One piston motor type, the planetary piston engine (rotation engine or Wankel engine) generates a rotational movement directly from the combustion process. Apart from being advantageous in terms of intermittent fuel feed, planetary piston motors offer further benefits over conventional reciprocating piston motors: they are lighter and have fewer components (there are no drive rods or crank shafts), their control is simpler and, due to the reduced friction losses at the cylinder faces, their efficiency is higher. However, this type of motor has not been fully accepted on the market due to the difficulty of sealing the three gas-tight chambers and the due to the eccentric bearing with the eccentric shaft.
Combustion turbines with combustion chambers for intermittent operation are also already known.
For instance, the Austrian patent specification AT 311 735 describes a combustion turbine for intermittent combustion in combustion chambers comprising inlet valves. Here, charging, combustion, and expansion of the fuel take place successively at periodical intervals. The inlet valves are actuated by a cam shaft driven by an electric motor. The electric motor is controlled electronically by means of temperature and pressure sensors located in the combustion chambers. Combustion turbines circumvent the high friction losses occurring in reciprocating piston engines due to the sealing elements, which account for an average 15% to 25% of the overall output (up to 40% in partial load operation). However, it has so far not been possible to realize satisfactory control of this combustion turbine.
AT 379 217 discloses a similar impulse-driven gas turbine, where a near-isochore combustion characteristic is ensured by the guide vane/runner combination and a controlled inlet system. The inlet system comprises a rotatable valve disc with openings and provided with a drive and controls. But so far it has not been possible technically to close the valve disc gas-tightly during the deflagration process. In addition, this combustion turbine has a complicated and labyrinthine structure, leading to power output losses and high manufacturing costs.
U.S. Pat. No. 2,557,198 A discloses a gas turbine with intermittent combustion, where the combustion chambers each have inlet and outlet valves. Two turbines are placed directly after the combustion chamber, with a chamber for compensating pressure fluctuations arranged between the turbines. Here, too, the use of valve discs causes sealing problems during operation; in addition, the off-gas side valve disc is exposed to very high temperatures, and this is why problems of wear and of heat deformation are to be expected at this point in particular.
DE 2 232 025 A1 discloses a gas turbine system—in particular a drive gear with constant volume combustion with a compressor—which consumes a lot of compression energy and consequently reduces the total efficiency considerably. The mechanically complex and interference-prone outlet valves at the combustion chamber are avoided. In a special embodiment of DE 2 232 025 A1, the combustion chamber room is divided into a primary and a secondary room, separated by a constriction. However, the constriction causes the combustion gases to flow back and, therefore, a difference in the filling of the primary and secondary chambers.
A further embodiment of DE 2 232 025 A1 shows a combustion turbine with combustion chambers located around the turbine. Such an arrangement leads to high turbine bearing temperatures and the need for cooling these. In addition, in such an arrangement, the combustion gases coming from the combustion chambers are diverted by 180° before hitting a compressor turbine. This diversion leads to unbalanced flow to the turbine and to power output losses.
DE 25 17 947 A1 discloses a turbo jet engine with combustion chamber for pulsating combustion, i.e. a drive gear working according to the constant volume combustion process, which operates in a periodical working process. FIG. 4 of DE 25 17 947 A1 discloses an embodiment in which a radial ejector, a pressure compensation chamber and a turbine are placed on the side of the outlet of the combustion chamber.